JP4897341B2 - Liquid crystal display - Google Patents

Description

  The present invention relates to a liquid crystal display device having wide viewing angle characteristics and excellent color reproducibility over a wide viewing angle.

  Liquid crystal display elements (also referred to as liquid crystal display panels), electroluminescence elements (separated into organic and inorganic types depending on the fluorescent material used, hereinafter referred to as EL elements), field emission devices (hereinafter referred to as FED elements), electrophoresis A display device using an element or the like displays an image without providing a space (vacuum housing) for two-dimensionally scanning an electron beam on the back side of a display screen like a cathode ray tube (CRT). . Therefore, these display devices are characterized by being thinner and lighter and having lower power consumption than a cathode ray tube. These display devices are sometimes referred to as flat panel displays because of their appearance characteristics.

  A display device using a liquid crystal display element, an EL element, a field emission element, or the like is a display using a cathode ray tube in various applications such as notebook computers, OA devices such as personal computer monitors, portable terminals, and televisions because of the above-described advantages over the cathode ray tube. It is becoming widespread instead of devices. Technological innovations such as viewing angle characteristics of liquid crystal display elements and EL elements and image quality improvement such as expansion of the display color reproducibility area are behind the progress of replacement of CRTs with flat panel displays. Recently, with the widespread use of multimedia and the Internet, there has been an improvement in video display performance. Furthermore, there are some fields that cannot be realized with CRT, such as electronic paper, large public, and advertising information displays.

The liquid crystal display device usually includes a liquid crystal cell, a drive circuit that sends a display signal voltage to the liquid crystal cell, a backlight (back light source), and a signal control system that sends an input image signal to the drive circuit. Call.
A liquid crystal cell usually comprises liquid crystal molecules, two substrates for enclosing and sandwiching the liquid crystal molecules, and an electrode layer for applying a voltage to the liquid crystal molecules, and a polarizing plate is disposed on the outer side thereof. A polarizing plate is usually composed of a protective film and a polarizing film, and is obtained by dyeing a polarizing film made of polyvinyl alcohol film with iodine, stretching, and laminating both surfaces with a protective film. In the transmissive liquid crystal display device, the polarizing plate is attached to both sides of the liquid crystal cell, and one or more optical compensation sheets may be disposed. In a reflective liquid crystal display device, usually, a reflector, a liquid crystal cell, one or more optical compensation sheets, and a polarizing plate are arranged in this order. The liquid crystal cell performs ON-OFF display depending on the alignment state of liquid crystal molecules, and can be applied to any of a transmission type, a reflection type, and a semi-transmission type.

When an optical compensation sheet whose optical properties are designed to an optimum value for each wavelength of light is used, a liquid crystal display device with little color change depending on the viewing angle can be provided. In these conventional liquid crystal display devices, an attempt is made to improve the color change by controlling the wavelength dispersion of the retardation of the optical compensation film (Patent Document 1). It has also been attempted to balance the display colors by changing the in-plane retardation value (Re) of the color filter for each color (Patent Document 2).
Japanese Patent Laid-Open No. 2002-221622 JP-A-5-196931

However, the liquid crystal display device cannot be improved at all wavelengths, and coloring from an oblique direction cannot be improved.
Therefore, an object of the present invention is to provide a liquid crystal display device having excellent color reproducibility in a wide viewing angle.
Further, when observing obliquely during black display, the so-called color shift problem of coloring blue or red has not been solved.
Therefore, an object of the present invention is to provide a liquid crystal display device in which color shift is not observed or color shift is reduced even when observed from an oblique direction during black display.

Means for solving the above problems are as follows.
[1] A component having at least one pair of substrates having electrodes arranged opposite to each other and a liquid crystal layer disposed between the substrates and controlled in orientation, and parallel to the substrate having the electrodes by the electrodes. A liquid crystal display device including at least a liquid crystal cell in which an electric field is formed and a pair of polarizing plates arranged with the liquid crystal layer interposed therebetween, wherein the liquid crystal cell includes three pixel regions and three picture elements. A color filter disposed on the elementary region, and Rth of color filters disposed on at least two of the three pixel regions are different from each other. Liquid crystal display device.
[2] When the main wavelengths taking the maximum transmittance corresponding to each of the three picture element regions of the color filter are λ ₁ , λ ₂ and λ ₃ (unit: nm) in order from the smallest, the color filter Wherein Rth satisfies the following formula (I): [1]
Formula (I): Rth (λ ₃ )> Rth (λ ₂ )
[3] When the main wavelengths taking the maximum transmittance of the color filters arranged on the three pixel regions are λ ₁ , λ _2, and λ ₃ (unit: nm) in order from the smallest, Rth of the color filter Satisfies the following formula (II): [1] or [2] liquid crystal display device:
Formula (II): Rth (λ ₁ )> Rth (λ ₂ )
[4] The liquid crystal display device according to any one of [1] to [3], wherein an electric field including a component parallel to the substrate is generated by a pixel electrode and a counter electrode arranged in different layers.
[5] An electric field including a component parallel to the substrate is generated by a pair of electrodes that are arranged in different layers and at least one of which is transparent, and an electrode to which no voltage is applied. ]-[4] liquid crystal display device.
[6] Both the pair of polarizing plates have a polarizing film and a protective film provided on at least one surface of the polarizing film, and the protective film is disposed between the liquid crystal cell and the polarizing film. The liquid crystal display device according to any one of [1] to [5].

  According to the present invention, a liquid crystal display device having excellent color reproducibility in a wide viewing angle can be provided. In addition, according to the present invention, it is possible to provide a liquid crystal display device in which color shift is not observed or color shift is reduced even when observed from an oblique direction during black display.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described in detail. In the present specification, “to” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value.
In this specification, Re (λ) and Rth (λ) represent in-plane retardation and retardation in the thickness direction at wavelength λ, respectively. Re (λ) is measured by making light having a wavelength of λ nm incident in the normal direction of the film in KOBRA 21ADH or WR (manufactured by Oji Scientific Instruments).
When the film to be measured is represented by a uniaxial or biaxial refractive index ellipsoid, Rth (λ) is calculated by the following method.
Rth (λ) is Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotation axis). The light is incident at a wavelength of λ nm in 10 degree steps from the normal direction to 50 degrees on one side with respect to the film normal direction (with the direction of the rotation axis as the rotation axis), and a total of 6 points are measured. KOBRA 21ADH or WR calculates based on the measured retardation value, the assumed value of the average refractive index, and the input film thickness value.
In the above, in the case of a film having a direction in which the retardation value is zero at a certain tilt angle with the slow axis in the plane from the normal direction as the rotation axis, the retardation value at a tilt angle larger than the tilt angle is After changing the sign to negative, KOBRA 21ADH or WR calculates.
In addition, the retardation value is measured from two inclined directions with the slow axis as the tilt axis (rotary axis) (in the absence of the slow axis, the arbitrary direction in the film plane is the rotary axis) Rth can also be calculated from the following formula (1) and formula (2) based on the value, the assumed value of the average refractive index, and the input film thickness value.

式（２）
Ｒｔｈ＝（（ｎｘ＋ｎｙ）／２−ｎｚ）×ｄ
注記：
式中、Ｒｅ（θ）は、法線方向から角度θ傾斜した方向におけるレタデーション値を表す。
また、式中、ｎｘは面内における遅相軸方向の屈折率を表し、ｎｙは面内においてｎｘに直交する方向の屈折率を表し、ｎｚはｎｘ及びｎｙに直交する方向の屈折率を表す。

Formula (2)
Rth = ((nx + ny) / 2−nz) × d
Note:
In the formula, Re (θ) represents a retardation value in a direction inclined by an angle θ from the normal direction.
In the formula, nx represents the refractive index in the slow axis direction in the plane, ny represents the refractive index in the direction orthogonal to nx in the plane, and nz represents the refractive index in the direction orthogonal to nx and ny. .

When the film to be measured cannot be expressed by a uniaxial or biaxial refractive index ellipsoid, that is, a film having no so-called optical axis, Rth (λ) is calculated by the following method.
Rth (λ) is the above-mentioned Re (λ), and the in-plane slow axis (determined by KOBRA 21ADH or WR) is the tilt axis (rotary axis) from −50 degrees to +50 degrees with respect to the film normal direction The light of wavelength λ nm is incident from each inclined direction in 10 degree steps and measured at 11 points, and KOBRA 21ADH or WR is measured based on the measured retardation value, the assumed average refractive index, and the input film thickness value. Is calculated.
In the above measurement, the assumed value of the average refractive index may be the value in the polymer handbook (John Wiley & Sons, Inc.) or various optical film catalogs. Those whose average refractive index is not known can be measured with an Abbe refractometer. Examples of the average refractive index values of main optical films are as follows:
Cellulose acylate (1.48), cycloolefin polymer (1.52), polycarbonate (1.59), polymethyl methacrylate (1.49), and polystyrene (1.59).
By inputting these assumed values of average refractive index and film thickness, KOBRA 21ADH or WR calculates nx, ny, and nz. Nz = (nx−nz) / (nx−ny) is further calculated from the calculated nx, ny, and nz.

In the present specification, regarding the angle, “+” means the counterclockwise direction, and “−” means the clockwise direction. Further, when the upper direction of the liquid crystal display device is 12 o'clock and the lower direction is 6 o'clock, the absolute value 0 ° direction in the angular direction means the 3 o'clock direction (right direction of the screen). Further, the “slow axis” means a direction in which the refractive index is maximized. The “visible light region” means 380 nm to 780 nm. Further, in this specification, the measurement wavelength such as the refractive index is a value at λ = 550 nm in the visible light region unless otherwise specified.
In addition, regarding the angle between each axis and direction, “parallel”, “vertical”, “45 °”, etc. means “approximately parallel”, “approximately vertical”, “approximately 45 °”, and is not exact. . Some deviation is allowed within the range to achieve each purpose. For example, “parallel” means that the crossing angle is approximately 0 °, and is −10 ° to 10 °, preferably −5 ° to 5 °, more preferably −3 ° to 3 °. “Vertical” means that the crossing angle is approximately 90 °, and is 80 ° to 100 °, preferably 85 ° to 95 °, more preferably 87 ° to 93 °. “45 °” means that the crossing angle is approximately 45 °, and is 35 ° to 55 °, preferably 40 ° to 50 °, more preferably 42 ° to 48 °.

  In this specification, “polarizing film (polarizing film)” and “polarizing film” are distinguished from each other, but “polarizing film” has a transparent protective film for protecting the polarizing film on at least one side of “polarizing film”. It shall mean a laminate.

  The present invention includes a pair of opposed substrates, at least one of which has an electrode, and a liquid crystal layer that is disposed between the substrates and whose orientation is controlled, and is parallel to the substrate having the electrode by the electrode. A liquid crystal display device having at least a liquid crystal cell in which an electric field including a component is formed and a pair of polarizing plates arranged with the liquid crystal layer interposed therebetween, wherein the liquid crystal cell includes three pixel regions and the three pixel regions. A color filter disposed on the picture element region, and Rth of color filters disposed on at least two of the three pixel element regions are different from each other. The present invention relates to a liquid crystal display device.

Λ ₁ , λ ₂ , and λ ₃ (unit: nm) in ascending order of the main wavelength taking the maximum transmittance of the color filter provided in each pixel region, the thickness direction of the color filter in each of these pixel regions From the viewpoint of the above-mentioned effect, it is preferable that the following formula (I) or (II) is satisfied, and that both the following formulas (I) and (II) are satisfied. More preferable in terms.
Formula (I): Rth (λ ₃ )> Rth (λ ₂ )
Formula (II): Rth (λ ₁ )> Rth (λ ₂ )

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
The liquid crystal display device shown in FIG. 1 includes a liquid crystal cell (9 to 13), an upper polarizing plate 21 (1 to 6) and a lower polarizing plate 22 (14 to 19) disposed between the liquid crystal cells, and a lower side. A backlight unit 20 including a lamp 20 a serving as a light source is provided on the outer side of the polarizing plate 22. The liquid crystal cells (9 to 13) include a liquid crystal cell upper substrate 9, a liquid crystal cell lower substrate 12, and a liquid crystal layer 11 sandwiched therebetween. The lower substrate 12 has an electrode layer (not shown in FIG. 1) on its opposite surface, and the electrode layer is configured to be able to supply an electric field parallel to the surface of the substrate 12 to the liquid crystal layer. Yes. The electrode layer is usually made of transparent indium tin oxide (ITO). An alignment layer (not shown in FIG. 1) for controlling the alignment of the liquid crystal molecules 11 is formed on the electrode layer of the substrate 12 and on the opposite surface of the substrate 9, and is applied to the surface when no driving voltage is applied. The orientation direction of the liquid crystal molecules 11 is controlled by the rubbing treatment directions 10 and 13.

  The shape, configuration, etc. of the electrode are not particularly limited, and any may be used as long as an electric field parallel to the substrate of the liquid crystal cell can be formed. In general, electrode configurations used in IPS mode and FFS mode liquid crystal display devices can be used. For example, a pixel electrode and a counter electrode arranged in different layers may be used, or at least one of the electrodes arranged in different layers may be composed of a pair of transparent electrodes and an electrode to which no voltage is applied. May be.

FIG. 2 schematically shows an OFF state and an ON state of an example of an IPS mode liquid crystal display device. Note that FIG. 2 shows a part of one pixel of the liquid crystal display device, and the relative sizes and the like of the respective members do not necessarily coincide with the actual ones. The same applies to FIG. 3 described later. In FIG. 2, members corresponding to the members in FIG. The same applies to FIG. 3 described later.
In FIG. 2, the plurality of linear electrode layers 24 formed on the opposing surface of the substrate 12 form an electric field 23 including an electric field component parallel to the plane of the substrate 12 when a voltage is applied. When no voltage is applied or when a low voltage is applied (OFF state), the liquid crystal molecules 11 are aligned in the longitudinal direction of the linear electrode layer 24 by the rubbing axes (10 and 13 in FIG. 1) of the opposing surfaces of the substrates 9 and 12. The orientation is controlled so as to have a slight angle with respect to. In this case, the dielectric anisotropy of the liquid crystal is assumed to be positive. In a state in which a voltage is applied to the linear electrode layer 24 (ON state), an electric field 23 including a component parallel to the substrates 9 and 12 is formed, and the liquid crystalline molecules 11 are aligned with their major axes coinciding with the electric field direction. . The angle formed by the electric field direction 23 with respect to the surface of the substrate 12 is preferably 20 degrees or less, more preferably 10 degrees or less, that is, substantially parallel. In the present specification, those of 20 degrees or less are generically expressed as a parallel electric field. Even if the linear electrode layer 24 is formed separately on the upper and lower substrates or formed only on one substrate, the effect does not change.

FIG. 3 schematically shows an OFF state and an ON state of an example of an FFS mode liquid crystal display device. In addition, the same number is attached | subjected to the member same as FIG. 2, and detailed description is abbreviate | omitted.
In FIG. 3, the electrode has a two-layer structure of an upper electrode layer 24 and a lower electrode layer 26, and the layers are arranged differently via an insulating layer 25. The electrode layer 26 may be an unpatterned electrode layer or an electrode layer patterned in a linear shape. The upper electrode layer 24 is preferably linear, but may be any of a mesh shape, a spiral shape, a dot shape, or the like as long as the electric field from the lower electrode layer 26 can pass therethrough. A floating electrode having a neutral potential may be further added. The insulating layer 25 may be a layer made of an inorganic material such as SiO or a nitride film, or a layer made of an organic material such as acrylic or epoxy. By applying a voltage to the upper electrode layer 24 and the lower electrode layer 26, an electric field 23 ′ containing a component parallel to the substrate 9 is formed. In the OFF state, as in the IPS mode, the liquid crystalline molecules 11 are aligned with their long axes coinciding with the rubbing axes (10 and 13 in FIG. 1) of the opposing surfaces of the substrates 9 and 12. On the other hand, in the ON state, an electric field 23 ′ including a component parallel to the substrates 9 and 12 is formed, and the liquid crystalline molecules 11 are aligned with their long axes coinciding with the electric field direction.

Although a detailed structure is not shown in FIG. 1, a color filter is disposed on the opposite surface of the upper substrate 9 or the lower substrate 12 of the liquid crystal cell, and the liquid crystal cell includes three picture element regions. For example, in the aspect in which the liquid crystal display device of FIG. 1 has a color filter composed of an R layer, a G layer, and a B layer, the three pixel regions are RGB regions in which the R layer, the G layer, and the B layer are respectively arranged. . Among these three colored layers, at least two colored layers, for example, the G layer and the R layer, or the G layer and the B layer have different Rths in the thickness direction. More preferably, the three colored layers have different Rths. The principal wavelengths λ _R , λ _G, and λ _B taking the maximum transmittances in the R region, the G region, and the B region are λ _B , λ _G, and λ _R in ascending order. When the retardation in the thickness direction of the color filter in the R region, G region, and B region is Rth, it is preferable that either of the following relational expressions is satisfied, and more preferable that both are satisfied.
Rth (λ _R )> Rth (λ _G )
Rth (λ _B )> Rth (λ _G )
In order to satisfy such a relational expression, for example, the thickness of the R layer (d _r ), the thickness of the G layer (d _g ), and the thickness of the B layer (d _b ) are different from each other (for example, _dr > d _g , d _A color filter that satisfies the relationship of _b > d _g may be used.

In FIG. 1 again, the liquid crystal cell is disposed between the upper polarizing plate 21 and the lower polarizing plate 22, and the upper polarizing plate 21 and the lower polarizing plate 22 are disposed with their absorption axes 4 and 17 orthogonal to each other. The When the upper polarizing plate 21 is a viewing side polarizing plate, the absorption axis 4 of the upper polarizing plate 21 is orthogonal to the extraordinary refractive index direction of the liquid crystalline molecules 11 in the liquid crystal cell when no voltage is applied (OFF state). It is preferable to laminate them as described above. The upper polarizing plate 21 has the polarizing film 3 and the protective films 1 and 5 disposed on the surface thereof, and the lower polarizing plate 22 includes the polarizing film 16 and the protective films 14 and 18 disposed on the surface thereof. And have.
The protective film disposed on the surface of the polarizing film is generally composed of a stretched film, and has a slow axis in the MD (Mechanical direction) direction or the direction coincident with the TD (Tenter direction) direction. The slow axis directions of the two protective films arranged on the surface of one polarizing film may be parallel to each other (2 and 6 in FIG. 1) like the upper polarizing plate 21 in FIG. Like the lower polarizing plate 22 in FIG. 1, they may be orthogonal to each other (15 and 19 in FIG. 1).

  In FIG. 1, consider a case where light is incident from a backlight unit 20 disposed outside the lower polarizing plate 22. In a non-driving state (OFF state) in which a driving voltage is not applied to the electrodes (not shown in FIG. 1), the liquid crystalline molecules 11 in the liquid crystal layer are substantially parallel to the surfaces of the substrates 9 and 12 and have their long axes. Are oriented substantially parallel to the rubbing axes 10 and 13. In this state, the light that has been brought into a predetermined polarization state by the polarization film 16 does not receive the birefringence effect of the liquid crystalline molecules 11, and as a result, is blocked by the absorption axis 4 of the polarization film 3. At this time, the display is black. On the other hand, in a driving state (ON state) in which a driving voltage is applied to an electrode (not shown in FIG. 1), an electric field including a component parallel to the substrate is formed, and the liquid crystalline molecules 11 have their long axes. Oriented in accordance with the direction of the electric field. As a result, the light having a predetermined polarization state by the polarization film 18 changes its polarization state due to the birefringence effect of the liquid crystalline molecules 11, and as a result, passes through the polarization film 3. At this time, the display is white. In the present invention, since the retardation Rth in the thickness direction of the color filter is made different for each pixel region, good color reproducibility can be obtained with a wide viewing angle, and coloring during black display, so-called color shift is reduced. Has been.

  In the IPS mode liquid crystal display device of FIG. 2, the alignment control direction of the liquid crystal layer (rubbing axes 10 and 13 in FIG. 1) is preferably arranged as the vertical direction of the display device, the 12 o'clock to 6 o'clock direction, The absorption axes 4 and 17 of the upper polarizing plate and the lower polarizing plate are also preferably arranged in the 12 o'clock to 6 o'clock direction and orthogonal to each other. Further, the slow axes 6 and 15 of the protective films 5 and 14 arranged between the polarizing films 3 and 16 and the liquid crystal layer are also arranged at 12 o'clock to 6 o'clock, and are arranged closer to each other. It is preferable to arrange them in parallel with the rubbing axis of the cell substrate. Such an arrangement is effective in reducing leakage light during black display and eliminating coloring in the viewing angle direction.

  Further, as shown in FIG. 1, an optically anisotropic layer 7 may be disposed between the liquid crystal cell side protective film 5 and the liquid crystal layer 11 of the upper polarizing plate 21. The retardation value of the optically anisotropic layer 7 is preferably set to be not more than twice the value of Δn · d of the liquid crystal layer 11. 1 shows a configuration in which the optically anisotropic layer 7 is disposed between the protective film 5 of the upper polarizing plate 21 and the liquid crystal layer 11, but the protective film 14 of the lower polarizing plate 22 and the liquid crystal layer are shown. 11 may be arranged between the two or both. Further, the retardation of the protective film 5 of the upper polarizing film 3 is less than the retardation of the protective film 14 of the lower polarizing film 16, and if Rth is 20 nm or more, it reduces leakage light during black display and eliminates coloring in the viewing angle direction. It is effective for.

  In the FFS mode liquid crystal display device shown in FIG. 3, the alignment control direction (rubbing axes 10 and 13 in FIG. 1) of the liquid crystal layer is preferably arranged as the horizontal direction of the display device, 3 o'clock to 9 o'clock. The absorption axes 4 and 17 of the polarizing plate and the lower polarizing plate are also preferably arranged in the 3 o'clock to 9 o'clock direction and orthogonal to each other. Further, the slow axes 6 and 11 of the protective films 5 and 14 arranged between the polarizing films 3 and 16 and the liquid crystal layer are also arranged at 3 o'clock to 9 o'clock, and the liquid crystals arranged closer to each other. It is preferable to arrange them in parallel with the rubbing axis of the cell substrate. Such an arrangement is effective in reducing leakage light during black display and eliminating coloring in the viewing angle direction. Further, as shown in FIG. 1, an optically anisotropic layer 7 may be disposed between the liquid crystal cell side protective film 5 and the liquid crystal layer 11 of the upper polarizing plate 21. The retardation value of the optically anisotropic layer 7 is preferably set to be not more than twice the value of Δn · d of the liquid crystal layer 11. 1 shows a configuration in which the optically anisotropic layer 7 is disposed between the protective film 5 of the upper polarizing plate 21 and the liquid crystal layer 11, but the protective film 14 of the lower polarizing plate 22 and the liquid crystal layer are shown. 11 may be arranged between the two or both.

The shape and arrangement of the electrodes are not limited to the configurations shown in FIGS. 2 and 3, and any shape electrodes and configurations conventionally used in the IPS mode and the FFS mode can be used. For example, in order to obtain a wider viewing angle, linear electrodes (sometimes referred to as “comb electrodes”) may be arranged in a zigzag shape. However, in this case, the orientation of the liquid crystal molecules in the liquid crystal layer is disturbed at the bent portion of the electrode, and the contrast of the display device may be lowered. In order to reduce this reduction in contrast, the slow axes (6 and 15 in FIG. 1) of the protective film (5 and 14 in FIG. 1) made of a cellulose acylate film or the like of the polarizing film (3 and 16 in FIG. 1) or the like are used. ) With the average orientation control direction (10 and 13 in FIG. 1) of the liquid crystal layer 11 within 10 °. When arranged in this way, the retardation unevenness of the liquid crystal layer due to the alignment disorder can be compensated, and the display uniformity can be improved. In addition, brightness unevenness during black display due to alignment disorder of liquid crystal molecules due to rubbing treatment can also be compensated for self-compensation for retardation unevenness by arranging a protective film with its slow axis intersecting the rubbing axis. Can be reduced.
The average direction of the alignment disorder of these liquid crystal molecules deviates from the original alignment control direction by about 5 to 15 °. Display unevenness can be reduced by compensating the retardation by crossing the slow axis of the protective film with the average orientation axis. As described above, when the protective film is arranged with its slow axis crossed, if the Re value of the protective film is large, even if the unevenness can be reduced, the black luminance absolute value increases and the contrast decreases. Since it may occur, it is preferable to use a protective film having a small Re.
Furthermore, as described above, an optically anisotropic layer is arranged, and unevenness can be similarly reduced by intersecting the slow axis, orientation control direction, and average orientation direction with the average orientation control direction of the liquid crystal layer within 10 °. can do.

In addition, the FFS mode has a tendency that the viewing angle tends to be narrower than that of the IPS mode, and the liquid crystal alignment disorder is large because a high electric field is applied at the electrode end. From these facts, the slow axis (6 and 15 in FIG. 1) of the protective film (5 and 14 in FIG. 1) made of cellulose film or the like is the average orientation control direction (10 and 13 in FIG. 1) of the liquid crystal layer 11. ) And within 10 °, the effect of reducing unevenness is further increased.
In both the IPS mode and the FFS mode liquid crystal display device, the slow axis of the protective film and the absorption axis of the polarizing film are present for either or both of the polarizing plate on the viewing side and the backlight side. It is preferable that the deviation is within the above range, and it is more preferable that the slow axis of the protective film and the absorption axis of the polarizing film are deviated within the above range.

Hereafter, each member etc. which can be used for the liquid crystal display device of this invention are demonstrated in detail.
[Liquid crystal materials]
The liquid crystal material constituting the liquid crystal layer used in the liquid crystal display device of the present invention is not particularly limited. In the liquid crystal display device having the configuration shown in FIG. 1, for example, nematic liquid crystal having a positive dielectric anisotropy Δε may be used as the liquid crystal material. The thickness (gap) of the liquid crystal layer is preferably more than 2.8 μm and less than 4.5 μm. When the retardation (Δn · d) of the liquid crystal layer is more than 0.25 μm and less than 0.32 μm, a transmittance characteristic having almost no wavelength dependency within the visible light range can be obtained more easily. Maximum transmittance can be obtained when the liquid crystal molecules are rotated 45 degrees from the rubbing direction to the electric field direction. The thickness (gap) of the liquid crystal layer is controlled by polymer beads. Of course, the same gap can be obtained with glass bead fiber or resin columnar spacers. The liquid crystal material LC is not particularly limited as long as it is a nematic liquid crystal. As the value of the dielectric anisotropy Δε is larger, the driving voltage can be reduced, and as the refractive index anisotropy Δn is smaller, the thickness (gap) of the liquid crystal layer can be increased, and the liquid crystal sealing time is shortened. In addition, gap variation can be reduced.

[Liquid Crystal Cell]
The liquid crystal cell used in the liquid crystal display device of the present invention has a pair of substrates, at least one of which has electrodes, and a liquid crystal layer that is disposed between the substrates and the alignment of which is controlled. It is preferable to form an alignment film for aligning liquid crystal molecules on both inner surfaces of the liquid crystal cell substrate. Moreover, it is preferable to form a color filter on any one of the opposing surfaces. Furthermore, a polarizing film may be disposed inside the liquid crystal cell, or an optically anisotropic layer that contributes to the optical compensation of the retardation of the liquid crystal layer may be disposed. In general, a columnar or spherical spacer is disposed to maintain a distance (cell gap) between two substrates. In addition, a reflector, a condenser lens, a brightness enhancement film, a light emitting layer, a fluorescent layer, a phosphorescent layer, an antireflection film, an antifouling film, a hard coat film, and the like may be disposed in the cell.

  A transparent glass substrate is generally used as the substrate for the liquid crystal cell, but a silicon glass substrate that is harder and can withstand high temperatures may be used. Further, a plastic substrate having excellent heat resistance or a substrate made of a polymer material may be used. A flexible or reelable display using a substrate made of a deformable material is also effective. Further, in the reflective display device, one of the substrates may be transparent, and a metal substrate such as stainless steel may be used for the other.

In the present invention, the liquid crystal display device includes three picture element regions. For example, in a liquid crystal display device that has a color filter and performs color display, the sub-pixels (picture element regions) of the three primary colors of light, red, green, and blue form one set and usually form one pixel. In some cases, one pixel is formed by sub-pixels of three or more colors. As one aspect of the present invention, there is a multi-gap aspect in which the cell gap is different in each color sub-pixel constituting one pixel.
Further, a structure called a multi-domain in which one pixel is divided into a plurality of regions may be used to adjust the color balance and average the viewing angle characteristics.

[Color filter]
In the present invention, it is preferable to dispose a color filter on one opposing surface of the pair of substrates of the liquid crystal cell. Although it does not restrict | limit especially about a color filter, For example, it is preferable to arrange | position the color filter containing each layer of red (R), green (G), and blue (B).
As described above, in the liquid crystal display device of the present invention, the liquid crystal cell includes three pixel regions, and Rths of color filters arranged in at least two of these pixel regions are different from each other. More preferably, the Rths of the color filters arranged in each of the three picture element regions are different from each other. One of the preferable means for achieving this configuration is that the thickness of the color filter arranged in at least two pixel regions is different from the thickness of the color filter arranged in each of the three pixel regions. There is a thing to do.
Accordingly, among the Rths of the color filters arranged in each of the three picture element regions, the Rths of the color filters arranged in each of the at least two picture element regions can be made different from each other. Can be achieved more effectively.

  The color filter can be produced, for example, by the following method. First, colored pixels, such as red, green, and blue, that match the purpose are formed on a transparent substrate. As a method of forming colored pixels such as red, green, and blue on a transparent substrate, the above-described staining method, printing method, or coloring resist method in which a colored photosensitive resin liquid is applied with a spin coater or the like and then patterned in a photolithography process. Furthermore, a laminating method or the like can be used as appropriate. For example, in a formation method including a coating process, a color filter having RGB layers having different thicknesses can be formed by adjusting the coating amount. In the case of using a laminate method, a color filter composed of RGB layers having different thicknesses can be formed by using transfer materials having different thicknesses.

When forming a black matrix using a black photosensitive resin, it is preferable to form it after forming the colored pixels. When a black matrix is first formed, only the resin surface is cured with a black photosensitive resin having a high optical density, so that the uncured resin is melted by the subsequent development process, particularly the repeated development process for forming colored pixels. This is because the formed matrix may be peeled off in an extreme case (referred to as side etching).
In contrast, if the black matrix is formed last, the periphery of the black matrix is surrounded by colored pixels, and the developer is difficult to penetrate from the cross section. There is a great advantage that it can be formed.
Furthermore, when the colored layer for forming the colored pixels is formed by the laminating method, if the black matrix is formed first, the place where the colored pixels are to be formed is closed in a substantially lattice pattern by the black matrix. Although there is a problem that air bubbles are sometimes easily involved, it is preferable to form a black matrix later because this problem does not occur.

  When the light transmittance of the colored pixel with respect to the photosensitive wavelength region of the black photosensitive resin exceeds 2%, it is preferable to add a light absorber or the like into the colored pixel in advance so that the transmittance is 2% or less. Various known compounds can be used as the light absorber used in this case. Examples include benzophenone derivatives (such as Michler's ketone), merocyanine compounds, metal oxides, benzotriazole compounds, and coumarin compounds. Among them, those that have good light absorption and retain 25% or more of light absorption performance even after heat treatment at 200 ° C. or higher are preferable. Specifically, titanium oxide, zinc oxide, benzotriazole compounds, coumarin compounds Compounds. Among these, coumarin compounds are particularly preferable from the viewpoints of both heat resistance and light absorption. The above-described heat treatment at 200 ° C. or higher is performed in order to further cure after forming each pixel.

  Next, a black photosensitive resin layer is provided on the entire surface of the transparent substrate so as to cover the pixel pattern. This is also a method of applying a black photosensitive resin liquid with a spin coater or a roll coater, or temporarily supporting the black photosensitive resin liquid in advance. An image forming material can be prepared by coating on the body, and the black photosensitive resin layer can be transferred onto the pixel pattern.

  Next, it exposes from the black photosensitive resin layer side through a photomask, and the black photosensitive resin layer of the light-shielding part (black matrix) in which a coloring pixel does not exist is hardened. The colored pixels are slightly misaligned due to the alignment error of the exposure tool and the thermal expansion of the substrate, the pixels themselves are thick and thin, and are not arranged at the designed dimensions. Is normal. This tendency is particularly strong for large-sized substrates. Therefore, when exposure is performed with a photomask according to the design pixel interval, a portion where the black matrix overlaps with the pixel or a portion where a gap is formed between the pixel is generated. Since the overlapped portion becomes a protrusion, and the portion where the gap is formed becomes light leakage, both are not preferable.

The color filter preferably satisfies the following conditions.
(I) 0 ≦ Re (630) ≦ 10 and | Rth (630) | ≦ 25
(II) | Re (400) −Re (700) | ≦ 10 and | Rth (400) −Rth (700) | ≦ 35
(In the above formulas (I) and (II), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value (nm) in the film thickness direction at the wavelength λnm. .)
Here, Re represents in-plane retardation, and this value is preferably as close to 0 as possible so as not to lower the front contrast ratio. Even if it is not 0, it is preferable that the slow axis of Re and the polarizing film absorption axis are parallel or orthogonal to each other.
Rth represents retardation in the thickness direction, does not affect the front contrast ratio reduction, and contributes to improvement of the color tone viewing angle in the oblique direction. By giving Rth of the above condition to the color filter, the optical compensation of the viewing angle can be performed more completely for each pixel, and the coloring phenomenon in the oblique direction of the liquid crystal display device in each display mode is improved (reduced). )be able to.

The retardation of the color filter may be adjusted by, for example, adding a retardation increasing agent or a reducing agent to the photosensitive layer or the colored layer, which is a constituent layer of the transfer material, when the color filter is prepared using a transfer material. .
Representative examples of the retardation increasing agent include compounds represented by the following formula and compounds similar thereto.

  An example of the retardation reducing agent is a compound represented by the following general formula (13).

In the general formula (13), R ¹¹ represents an alkyl group or an aryl group, and R ¹² and R ¹³ each independently represent a hydrogen atom, an alkyl group, or an aryl group. Further, it is particularly preferable that the total number of carbon atoms of R ¹¹ , R ¹² and R ¹³ is 10 or more. R ¹¹ , R ¹² and R ¹³ may have a substituent, and the substituent is preferably a fluorine atom, an alkyl group, an aryl group, an alkoxy group, a sulfone group or a sulfonamide group, an alkyl group, an aryl group, Alkoxy groups, sulfone groups and sulfonamido groups are particularly preferred. Further, the alkyl group may be linear, branched or cyclic, and preferably has 1 to 25 carbon atoms, more preferably 6 to 25, and more preferably 6 to 20 (For example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, t-butyl, amyl, isoamyl, t-amyl, hexyl, cyclohexyl, heptyl, octyl, bicyclo Octyl, nonyl, adamantyl, decyl, t-octyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, didecyl) are particularly preferred . As the aryl group, those having 6 to 30 carbon atoms are preferable, and those having 6 to 24 carbon atoms (for example, phenyl group, biphenyl group, terphenyl group, naphthyl group, binaphthyl group, triphenylphenyl group) are particularly preferable.

[Optical compensation sheet]
The liquid crystal display device of the present invention may have an optical compensation sheet. Optical compensation sheets are used in various liquid crystal display devices in order to eliminate image coloring and expand the viewing angle. As the optical compensation sheet, a stretched birefringent polymer film has been conventionally used. Instead of an optical compensation sheet comprising a stretched birefringent film, an optical compensation sheet having an optically anisotropic layer formed from a low-molecular or high-molecular liquid crystalline compound on a transparent support is used, or from a stretched birefringent film In addition to the optical compensation sheet, it has been proposed to use an optical compensation sheet having an optically anisotropic layer formed from a low-molecular or high-molecular liquid crystalline compound. Since liquid crystal compounds have various alignment forms, the use of liquid crystal compounds makes it possible to realize optical properties that cannot be obtained only with conventional stretched birefringent polymer films. Furthermore, it can also function as a protective film for a polarizing plate. The present optical compensation sheet itself can be used as a substrate for a liquid crystal cell, and a plastic substrate can also serve as an optical compensation sheet. It is also possible to form this optical compensation sheet inside the liquid crystal cell.

  The optical properties of the optical compensation sheet are determined according to the optical properties of the liquid crystal cell, specifically, the display mode differences as described above. When a liquid crystal compound is used, optical compensation sheets having various optical properties corresponding to various display modes of the liquid crystal cell can be produced. Various optical compensation sheets using liquid crystal compounds in the form of rods, spheroids, or disks corresponding to various display modes have already been proposed. For example, the IPS mode optical compensation sheet can compensate for the viewing angle dependency of the polarizing plate to reduce the luminance of black display in all directions and improve the viewing angle characteristic of contrast. Furthermore, the optical property of the optical compensation sheet is designed to be an optimum value for each wavelength of light, thereby providing a liquid crystal display device having a wide visual field characteristic with little color change. It is particularly effective when combined with multi-gap and multi-domain. In addition, the viewing angle can be narrowed so that the display can be observed only from a specific direction, instead of enlarging the viewing angle.

Hereinafter, an optical compensation sheet having an optically anisotropic layer formed from a composition containing a liquid crystalline compound on a support made of a polymer film or the like will be described in detail as an optical compensation sheet that can be used in the present invention. .
<< Optically anisotropic layer >>
The optically anisotropic layer is formed by disposing a composition containing a liquid crystalline compound on a surface, for example, a surface subjected to rubbing treatment along a predetermined rubbing axis or the like, and depending on the rubbing axis, molecules of the liquid crystalline compound Can be oriented and fixed in the oriented state. Examples of the liquid crystalline compound used for forming the optically anisotropic layer include both a rod-like liquid crystalline compound and a discotic liquid crystalline compound. The rod-like liquid crystal compound and the discotic liquid crystal compound may be a polymer liquid crystal or a low-molecular liquid crystal, and further include those in which the low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity.

《Bar-shaped liquid crystalline molecules》
Examples of rod-like liquid crystalline molecules include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoic acid esters, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines. , Phenyldioxanes, tolanes and alkenylcyclohexylbenzonitriles are preferably used.
The rod-like liquid crystalline molecule includes a metal complex. In addition, a liquid crystal polymer containing a rod-like liquid crystalline molecule in a repeating unit can also be used as the rod-like liquid crystalline molecule. In other words, the rod-like liquid crystal molecule may be bonded to a (liquid crystal) polymer.
For rod-like liquid crystalline molecules, see Chapter 4, Chapter 7 and Chapter 11 in the Chemistry of the Quarterly Chemical Review Vol. 22 Liquid Crystal Chemistry (1994) edited by the Chemical Society of Japan, and the 142nd Committee of the Japan Society for the Promotion of Science. Described in Chapter 3. The birefringence of the rod-like liquid crystal molecule is preferably in the range of 0.001 to 0.7.

  The rod-like liquid crystalline molecule preferably has a polymerizable group in order to fix its alignment state. The polymerizable group is preferably a radically polymerizable unsaturated group or a cationically polymerizable group. Specifically, for example, the polymerizable groups described in paragraphs [0064] to [0086] of JP-A-2002-62427 are described. Group and a polymerizable liquid crystal compound.

《Discotic liquid crystalline compound》
The discotic liquid crystalline compound is aligned substantially perpendicular to the polymer film surface. Discotic liquid crystalline compounds are disclosed in various documents (C. Destrade et al., Mol. Crysr. Liq. Cryst., Vol. 71, page 111 (1981); edited by The Chemical Society of Japan, Quarterly Chemical Review, No. 22, Liquid Crystal Chemistry, Chapter 5, Chapter 10 Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., Page 1794 (1985); J. Zhang et al., J Am. Chem. Soc., Vol. 116, page 2655 (1994)) can be widely used.

The discotic liquid crystalline compound preferably has a polymerizable group, for example, as described in JP-A-8-27284 so that it can be fixed by polymerization. For example, a structure in which a polymerizable group is bonded as a substituent to the discotic core of a discotic liquid crystalline compound can be considered, but if a polymerizable group is directly connected to the discotic core, the alignment state can be maintained in the polymerization reaction. It becomes difficult. Therefore, a structure having a linking group between the discotic core and the polymerizable group is preferable. That is, the discotic liquid crystalline compound having a polymerizable group is preferably a compound represented by the following formula (III).
Formula (III) D (-LP) _n
In formula (III), D is a discotic core, L is a divalent linking group, P is a polymerizable group, and n is an integer of 4 to 12.

  Preferred specific examples of the discotic core (D), the divalent linking group (L), and the polymerizable group (P) in the formula (III) are (D1) described in JP-A No. 2001-4837, respectively. To (D15), (L1) to (L25), and (P1) to (P18), and the contents described in the publication can be preferably used.

  In the optically anisotropic layer, the molecules of the liquid crystalline compound are preferably aligned substantially perpendicular to the layer surface. The rod-like liquid crystalline molecules are preferably oriented with their major axes being substantially perpendicular to the layer surface, and the discotic liquid crystalline molecules are oriented with their disc surfaces substantially perpendicular to the layer surface. preferable. The term “substantially perpendicular” means that the average angle (average inclination angle) between the major axis of the rod-like liquid crystal compound or the disc surface of the discotic liquid crystal molecule and the layer surface is in the range of 70 ° to 90 °. . The liquid crystalline molecules are preferably substantially uniformly aligned, more preferably fixed in a substantially uniformly aligned state, and the liquid crystalline compound is fixed by a polymerization reaction. Most preferably.

  The optically anisotropic layer is preferably formed by disposing a liquid crystal compound and, if desired, a composition containing the following polymerization initiator and other additives on the alignment film. The composition may be prepared as a coating solution. As a solvent used for preparing the coating solution, an organic solvent is preferably used. Examples of organic solvents include amides (eg, N, N-dimethylformamide), sulfoxides (eg, dimethyl sulfoxide), heterocyclic compounds (eg, pyridine), hydrocarbons (eg, benzene, hexane), alkyl halides (eg, , Chloroform, dichloromethane), esters (eg, methyl acetate, butyl acetate), ketones (eg, acetone, methyl ethyl ketone), ethers (eg, tetrahydrofuran, 1,2-dimethoxyethane). Alkyl halides and ketones are preferred. Two or more organic solvents may be used in combination. The coating liquid can be applied by a known method (eg, extrusion coating method, direct gravure coating method, reverse gravure coating method, die coating method).

<Immobilization of alignment state of liquid crystalline compounds>
The aligned liquid crystal compound molecules are preferably fixed while maintaining the alignment state. The immobilization is preferably carried out by a polymerization reaction of a polymerizable group introduced into the liquid crystal compound. The polymerization reaction includes a thermal polymerization reaction using a thermal polymerization initiator and a photopolymerization reaction using a photopolymerization initiator, and a photopolymerization reaction is more preferable. Examples of photopolymerization initiators include α-carbonyl compounds (described in US Pat. Nos. 2,367,661 and 2,367,670), acyloin ether (described in US Pat. No. 2,448,828), α-hydrocarbon substitution. Aromatic acyloin compounds (described in US Pat. No. 2,722,512), polynuclear quinone compounds (described in US Pat. Nos. 3,046,127 and 2,951,758), combinations of triarylimidazole dimers and p-aminophenyl ketone (US Patent No. 3549367), acridine and phenazine compounds (JP-A-60-105667, US Pat. No. 4,239,850) and oxadiazole compounds (US Pat. No. 4,221,970) Is included.

The amount of the photopolymerization initiator used is preferably 0.01 to 20% by mass, more preferably 0.5 to 5% by mass, based on the solid content of the coating solution. Light irradiation for the polymerization of the liquid crystalline compound is preferably performed using ultraviolet rays. The irradiation energy is preferably ^{20mJ / cm 2 ~50J / cm 2} , further preferably 100 to 800 mJ / cm ^2. In order to accelerate the photopolymerization reaction, light irradiation may be performed under heating conditions. The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, and more preferably 0.5 to 5 μm.

<< Vertical alignment film >>
In order to align the liquid crystalline compound vertically on the alignment film side, it is important to reduce the surface energy of the alignment film. Specifically, the surface energy of the alignment film is lowered by the functional group of the polymer, thereby bringing the liquid crystalline compound into a standing state. As the functional group for reducing the surface energy of the alignment film, a hydrocarbon group having 10 or more fluorine atoms and carbon atoms is effective. In order to make a fluorine atom or a hydrocarbon group exist on the surface of the alignment film, it is preferable to introduce a fluorine atom or a hydrocarbon group into the side chain rather than the main chain of the polymer. The fluoropolymer preferably contains fluorine atoms in a proportion of 0.05 to 80% by mass, more preferably in a proportion of 0.1 to 70% by mass, and in a proportion of 0.5 to 65% by mass. More preferably, it is most preferable to contain in the ratio of 1-60 mass%. The hydrocarbon group is an aliphatic group, an aromatic group or a combination thereof. The aliphatic group may be cyclic, branched or linear. The aliphatic group is preferably an alkyl group (may be a cycloalkyl group) or an alkenyl group (may be a cycloalkenyl group). The hydrocarbon group may have a substituent that does not exhibit strong hydrophilicity, such as a halogen atom. The number of carbon atoms of the hydrocarbon group is preferably 10 to 100, more preferably 10 to 60, and most preferably 10 to 40. The main chain of the polymer preferably has a polyimide structure or a polyvinyl alcohol structure.

  Polyimide is generally synthesized by a condensation reaction of tetracarboxylic acid and diamine. A polyimide corresponding to a copolymer may be synthesized using two or more kinds of tetracarboxylic acids or two or more kinds of diamines. The fluorine atom or hydrocarbon group may be present in the repeating unit derived from tetracarboxylic acid, may be present in the repeating unit derived from diamine, or may be present in both repeating units. When introducing a hydrocarbon group into polyimide, it is particularly preferable to form a steroid structure in the main chain or side chain of the polyimide. The steroid structure present in the side chain corresponds to a hydrocarbon group having 10 or more carbon atoms, and has a function of vertically aligning the liquid crystalline compound. In this specification, the steroid structure is a cyclopentanohydrophenanthrene ring structure or a ring structure in which a part of the ring bond is a double bond in the range of an aliphatic ring (a range that does not form an aromatic ring). means.

  Further, as a means for vertically aligning the molecules of the liquid crystal compound, a method of mixing an organic acid with a polymer of polyvinyl alcohol or polyimide can be suitably used. As the acid to be mixed, carboxylic acid, sulfonic acid and amino acid are preferably used. You may use what shows the acidity among the below-mentioned air interface aligning agent. The mixing amount is preferably 0.1% by mass to 20% by mass and more preferably 0.5% by mass to 10% by mass with respect to the polymer.

  For uniform alignment of the molecules of the discotic liquid crystalline compound, it is preferable to control the alignment direction by rubbing the vertical alignment film. The rubbing treatment may be performed by rubbing the surface of the polymer layer several times in a certain direction with paper or cloth. On the other hand, the molecules of the rod-like liquid crystal compound can be aligned without performing rubbing treatment. In any alignment film, the alignment film preferably has a polymerizable group for the purpose of improving the adhesion between the optically anisotropic layer and the transparent support. The polymerizable group can be introduced by introducing a repeating unit having a polymerizable group in the side chain or as a substituent of a cyclic group. It is more preferable to use an alignment film that forms a chemical bond with the molecules of the liquid crystal compound at the interface. Such an alignment film is described in JP-A-9-152509. The thickness of the alignment film is preferably 0.01 to 5 μm, and more preferably 0.05 to 1 μm. In addition, after aligning the molecules of the liquid crystalline compound using the alignment film, the molecules of the liquid crystalline compound are fixed in the alignment state to form an optically anisotropic layer, and only the optically anisotropic layer is formed on the polymer film. The image may be transferred onto a support such as.

<Air interface alignment agent>
Ordinary liquid crystal compound molecules have the property of being tilted and aligned on the air interface side, so in order to obtain a uniformly vertically aligned state, the liquid crystal compound molecules are also vertically aligned on the air interface side. It is necessary. For this purpose, the composition (coating liquid) contains a compound that is unevenly distributed on the air interface side and acts to vertically align the molecules of the liquid crystalline compound by its excluded volume effect or electrostatic effect. . The action of vertically aligning the molecules of the liquid crystal compound corresponds to the action of reducing the tilt angle of the director, that is, the angle formed by the director and the air side surface, in the molecule of the discotic liquid crystal compound. Compounds that reduce the angle of inclination of the director of the discotic liquid crystalline molecule include those in which a plurality of F atoms are bonded in order to be unevenly distributed on the air interface side, and those in which a sulfonyl group or a carboxyl group is bonded. In addition, a compound in which a rigid structural unit that gives an excluded volume effect such that the liquid crystal molecules are aligned perpendicularly is bonded preferably.

  In addition to the exemplified compounds, compounds described in JP-A Nos. 2002-20363 and 2002-129162 can be used as the air interface alignment agent. In addition, paragraph numbers 0072 to 0075 of Japanese Patent Application Laid-Open No. 2004-53981, paragraph numbers 0038 to 0048 and 0048 to 0049 of Japanese Patent Application No. 2002-243600, paragraph numbers 0037 to 0039 of Japanese Patent Application No. 2002-262239, The matters described in paragraph Nos. 0071 to 0078 of JP 2004-4688 A can also be applied to the present invention as appropriate.

  When using an air interface alignment agent, it is preferable that the addition amount of the air interface alignment agent in the composition for optically anisotropic layer formation is 0.05 mass%-5 mass%. Moreover, when using a fluorine saturation type | system | group air interface aligning agent, it is preferable that it is 1 mass% or less.

  The in-plane retardation (Re) of the entire optical compensation sheet is preferably 20 to 200 nm. The retardation in the thickness direction (Rth) of the entire optical compensation sheet is preferably 50 to 500 nm.

The optical compensation sheet may have a support made of a polymer film that supports the optically anisotropic layer. The polymer film used for the support is not particularly limited, and films such as cellulose acylate, polycarbonate, polysulfone, polyethersulfone, polyacrylate, polymethacrylate, norbornene resin are used. These polymer films may be stretched polymer films or a combination of a coating-type polymer layer and a polymer film. These polymer films are preferably manufactured in the same direction (roll-to-roll) in the longitudinal direction of the film at the time of manufacture in order to improve productivity and shape stability when temperature and humidity change.
In the embodiment in which the support of the optically anisotropic layer also serves as a protective film for the polarizing plate, the support is preferably a cellulose acylate film described later.

  Since the liquid crystal compound has various alignment forms, the optically anisotropic layer formed using the liquid crystal compound exhibits a desired optical property by a single layer or a laminate of a plurality of layers. That is, the optical compensation sheet may be an aspect that satisfies the optical characteristics required for the optical compensation sheet in the whole of the support, one or more optically anisotropic layers formed on the support, and the laminate. Good. In such an aspect, the retardation of the entire optical compensation sheet can be adjusted by both the optical characteristics of the optically anisotropic layer and the optical characteristics of the support made of the polymer film.

  In the liquid crystal display device of the present invention, an optical compensation sheet made of a stretched birefringent polymer film may be used. By adjusting the stretching conditions and the like, a stretched birefringent polymer film that satisfies the optical characteristics required for the optical compensation sheet can be produced.

[Polarizer]
In the present invention, a polarizing plate having a polarizing film and a pair of protective films sandwiching the polarizing film, or a polarizing film and a protective film provided on at least one side of the polarizing film may be used. For example, a polarizing film obtained by dyeing a polarizing film made of a polyvinyl alcohol film or the like with iodine, stretching and laminating both surfaces with a protective film can be used. A polarizing film may be disposed inside the liquid crystal cell. In the liquid crystal display device of the present invention, it is preferable that a pair of polarizing plates each having a polarizing film and a pair of protective films sandwiching the polarizing film are disposed with the liquid crystal cell interposed therebetween.

《Polarized film》
Examples of the polarizing film (sometimes referred to as “linearly polarizing film”) include an iodine-based polarizing film, a dye-based polarizing film using a dichroic dye, and a polyene-based polarizing film. The iodine-based polarizing film and the dye-based polarizing film are generally produced using a polyvinyl alcohol-based film.

  The linear polarizing film is manufactured by Optiva Inc. And a polarizing film comprising a binder and iodine or a dichroic dye is preferable. The iodine and the dichroic dye in the linearly polarizing film exhibit deflection performance by being oriented in the binder. It is preferable that the iodine and the dichroic dye are aligned along the binder molecule, or the dichroic dye is aligned in one direction by self-assembly such as liquid crystal. Currently, commercially available polarizers are made by immersing a stretched polymer in a solution of iodine or dichroic dye in a bath and allowing iodine or dichroic dye to penetrate into the binder. Is common.

  In a commercially available polarizing film, iodine or a dichroic dye is distributed about 4 μm (about 8 μm on both sides) from the polymer surface, and a thickness of at least 10 μm is necessary to obtain sufficient polarizing performance. The penetrability can be controlled by the solution concentration of iodine or dichroic dye, the temperature of the bath, and the immersion time. As described above, the lower limit of the binder thickness is preferably 10 μm. The upper limit of the thickness is preferably as thin as possible from the viewpoint of light leakage of the liquid crystal display device. It is preferably not more than a commercially available polarizing plate (about 30 μm), preferably 25 μm or less, and more preferably 20 μm or less. When the thickness is 20 μm or less, the light leakage phenomenon is not observed on a 17-inch liquid crystal display device.

  The binder of the polarizing film may be cross-linked. As the crosslinked binder, a polymer that can be crosslinked per se can be used. A polarizing film can be formed by reacting a polymer having a functional group or a binder obtained by introducing a functional group into a polymer between the binders by light, heat, or pH change. Moreover, you may introduce | transduce a crosslinked structure into a polymer with a crosslinking agent. Crosslinking is generally performed by applying a coating liquid containing a polymer or a mixture of a polymer and a crosslinking agent to the surface and then heating. Since it is only necessary to ensure durability at the stage of the final product, the crosslinking treatment may be performed at any stage until the final polarizing plate is obtained.

  As the binder for the polarizing film, either a polymer that can be crosslinked by itself or a polymer that is crosslinked by a crosslinking agent can be used. Most preferred are polyvinyl alcohol and modified polyvinyl alcohol. The modified polyvinyl alcohol is described in JP-A-8-338913, JP-A-9-152509, and JP-A-9-316127. Two or more kinds of polyvinyl alcohol and modified polyvinyl alcohol may be used in combination.

  In the polarizing film, the addition amount of the binder crosslinking agent is preferably 0.1 to 20% by mass with respect to the binder. The orientation of the polarizing element and the wet heat resistance of the polarizing film are improved.

The alignment film contains a certain amount of a crosslinking agent that has not reacted even after the crosslinking reaction has been completed. However, the amount of the remaining crosslinking agent is preferably 1.0% by mass or less and more preferably 0.5% by mass or less in the alignment film. In this way, the polarization degree does not decrease even when the polarizing film is incorporated into a liquid crystal display device and used for a long time or left in a high temperature and high humidity atmosphere for a long time.
The crosslinking agent is described in US Reissue Patent 23297. Boron compounds (eg, boric acid, borax) can also be used as a crosslinking agent.

As the dichroic dye, an azo dye, a stilbene dye, a pyrazolone dye, a triphenylmethane dye, a quinoline dye, an oxazine dye, a thiazine dye, or an anthraquinone dye is used. The dichroic dye is preferably water-soluble. The dichroic dye preferably has a hydrophilic substituent (eg, sulfo, amino, hydroxyl).
As an example of a dichroic dye, the compound as described in page 58 of the said technical number 2001-1745 is mentioned, for example.

  When the polarizing film is produced by a stretching method, the stretching ratio is preferably 2.5 to 30.0 times, and more preferably 3.0 to 10.0 times. Stretching can be performed by dry stretching in air. Moreover, you may implement wet extending | stretching in the state immersed in water. The stretch ratio of dry stretching is preferably 2.5 to 5.0 times, and the stretch ratio of wet stretching is preferably 3.0 to 10.0 times. The stretching step may be performed in several steps including oblique stretching. By dividing into several times, it is possible to stretch more uniformly even at high magnification. Before the oblique stretching, a slight stretching (a degree to prevent shrinkage in the width direction) may be performed horizontally or vertically. Stretching can be performed by performing tenter stretching in biaxial stretching in different steps. The biaxial stretching is the same as the stretching method performed in normal film formation. In biaxial stretching, stretching is performed at different speeds on the left and right, so that the thickness of the binder film before stretching needs to be different on the left and right. In casting film formation, the flow rate of the binder solution can be differentiated between the left and right sides by tapering the die.

  When the polarizing film is produced by a rubbing method, a rubbing treatment method widely adopted as a liquid crystal alignment treatment step for LCD can be applied. That is, orientation is obtained by rubbing the surface of the film in a certain direction using paper, gauze, felt, rubber, nylon, or polyester fiber. Generally, it is carried out by rubbing several times using a cloth in which fibers having a uniform length and thickness are planted on average. It is preferable to carry out using a rubbing roll in which the roundness, cylindricity, and deflection (eccentricity) of the roll itself are all 30 μm or less. The wrap angle of the film on the rubbing roll is preferably 0.1 to 90 °. However, as described in JP-A-8-160430, a stable rubbing treatment can be obtained by winding 360 ° or more.

  When the process of rubbing a long film is included, it is preferable to transport the film at a speed of 1 to 100 m / min with a constant tension by a transport device. The rubbing roll is preferably rotatable in the horizontal direction with respect to the film traveling direction for setting an arbitrary rubbing angle. It is preferable to select an appropriate rubbing angle in the range of 0 to 60 °.

  The polarizing film used in the present invention preferably has an absorption axis having a predetermined angle with respect to the longitudinal direction. When the absorption axis of the polarizing film has a predetermined angle with respect to the longitudinal direction, it can be easily pasted with a roll-to-roll when pasting with a protective film whose slow axis coincides with the longitudinal direction. it can. For example, as described in JP 2003-207628 A, a pair of protective films prepared in a long shape are bonded to both sides of a polarizing film prepared in a long shape, and a long laminate is obtained. Through a process of cutting (punching) into a desired size, a single plate polarizing plate can be obtained with high yield.

  The moisture permeability of the protective film is important for improving the productivity of the polarizing plate. That is, the polarizing film and the protective film are bonded together with a water-based adhesive, and the adhesive solvent is dried by diffusing in the protective film. The higher the moisture permeability of the protective film, the faster the drying and the higher the productivity. However, if the protective film is too high, moisture will enter the polarizing film depending on the usage environment (high humidity) of the liquid crystal display device. There is a tendency for the polarization ability to decrease.

《Protective film》
As the protective film, it is preferable to use a protective film provided on at least one surface of the polarizing film that satisfies one of the following conditions (3) and (4).
(3) Cellulose acylate film satisfying the following formulas (I) and (II) (I) 0 ≦ Re (630) ≦ 10 and | Rth (630) | ≦ 25
(II) | Re (400) −Re (700) | ≦ 10 and | Rth (400) −Rth (700) | ≦ 35
(In the above formulas (I) and (II), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value (nm) in the film thickness direction at the wavelength λnm. .)
(4) Protective film (III) (Rth _(A) -Rth ₍₀₎ ) containing a compound that lowers Rth such that Rth in the film thickness direction of the protective film satisfies the following formulas (III) and (IV) /A≦−1.0
(IV) 0.01 ≦ A ≦ 30
(In the formulas (III) and (IV), Rth _(A) represents Rth (unit: nm) of a protective film containing a compound that reduces Rth, and Rth ₍₀₎ is the protective film, R represents the Rth (nm) of the film not containing the compound that reduces Rth, and A represents the mass (%) of the compound that reduces Rht when the mass of the film raw material polymer is 100.)
The above formulas (III) and (IV) are (III-I) (Rth _(A) -Rth ₍₀₎ ) /A≤-2.0
(IV-I) 0.1 ≦ A ≦ 20
More preferably.
Here, the polymer of a film raw material means a raw material polymer of a main component constituting the film, and examples thereof include cellulose acylate.

  Examples of cellulose as a cellulose acylate raw material include cotton linter and wood pulp (hardwood pulp, conifer pulp). Cellulose acylate obtained from any raw material cellulose can be used, and in some cases, a mixture may be used. . Detailed descriptions of these raw material celluloses can be found in, for example, Plastic Materials Course (17) Fibrous Resin (Maruzawa, Uda, Nikkan Kogyo Shimbun, published in 1970) and Invention Association Open Technical Report 2001-1745 (page 7). To page 8) can be used, and the cellulose is not particularly limited.

  The cellulose acylate that can be used in the present invention is, for example, one obtained by acylating a hydroxyl group of cellulose, and the substituent can be any acetyl group having 2 to 22 carbon atoms of the acyl group. The degree of substitution of the cellulose acylate that can be used in the present invention with the hydroxyl group of the cellulose is not particularly limited, but the degree of binding of acetic acid and / or a fatty acid having 3 to 22 carbon atoms to replace the cellulose with a hydroxyl group is measured, The degree of substitution is obtained by calculation. As a measuring method, it can carry out according to ASTM D-817-91.

  In the cellulose acylate, the degree of substitution of the cellulose with a hydroxyl group is not particularly limited, but the degree of acyl substitution with the hydroxyl group of cellulose is preferably 2.50 to 3.00. Furthermore, the substitution degree is more preferably 2.75 to 3.00, and further preferably 2.85 to 3.00.

  Among the acetic acid and / or fatty acid having 3 to 22 carbon atoms substituted for the hydroxyl group of cellulose, the acyl group having 2 to 22 carbon atoms may be an aliphatic group or an allyl group, and may be a single or a mixture of two or more types. Good. Examples thereof include cellulose alkylcarbonyl ester, alkenylcarbonyl ester, aromatic carbonyl ester and aromatic alkylcarbonyl ester. Each of these may further have a substituted group. These preferred acyl groups include acetyl, propionyl, butanoyl, heptanoyl, hexanoyl, octanoyl, decanoyl, dodecanoyl, tridecanoyl, tetradecanoyl, hexadecanoyl, octadecanoyl , Iso-butanoyl group, tert-butanoyl group, cyclohexanecarbonyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like. Among these, acetyl group, propionyl group, butanoyl group, dodecanoyl group, octadecanoyl group, tert-butanoyl group, oleoyl group, benzoyl group, naphthylcarbonyl group, cinnamoyl group and the like are preferable, and acetyl group, propionyl group, butanoyl group are preferable. Groups are more preferred.

  Among the acyl substituents substituted on the hydroxyl group of cellulose described above, in the case of substantially consisting of at least two kinds of acetyl group, propionyl group and butanoyl group, the total substitution degree is 2.50 to 3.00 In particular, the optical anisotropy of the cellulose acylate film can be lowered, which is preferable. The degree of acyl substitution is more preferably 2.60 to 3.00, still more preferably 2.65 to 3.00.

  The degree of polymerization of cellulose acylate preferably used in the present invention is 180 to 700 in terms of viscosity average polymerization degree, and in cellulose acetate, 180 to 550 is more preferable, 180 to 400 is more preferable, and 180 to 350 is particularly preferable. . By setting the degree of polymerization to a certain value or less, the viscosity of the cellulose acylate dope solution is increased, and it is possible to more effectively prevent film production from becoming difficult due to casting. By setting the degree of polymerization to a certain level or more, it is possible to more effectively prevent the strength of the produced film from being lowered. The average degree of polymerization can be measured, for example, by the intrinsic viscosity method of Uda et al. (Kazuo Uda, Hideo Saito, Journal of Textile Society, Vol. 18, No. 1, pages 105-120, 1962). This method is described in detail in JP-A-9-95538.

  Further, the molecular weight distribution of cellulose acylate preferably used in the present invention is evaluated by gel permeation chromatography, and its polydispersity index Mw / Mn (Mw is mass average molecular weight, Mn is number average molecular weight) is small, and molecular weight distribution. Is preferably narrow. The specific value of Mw / Mn is preferably 1.0 to 3.0, more preferably 1.0 to 2.0, and most preferably 1.0 to 1.6. preferable.

When the low molecular component is removed, the average molecular weight (degree of polymerization) increases, but the viscosity becomes lower than that of normal cellulose acylate, which is useful. Cellulose acylate having a small amount of low molecular components can be obtained by removing low molecular components from cellulose acylate synthesized by a usual method. The removal of the low molecular component can be carried out by washing the cellulose acylate with an appropriate organic solvent. In addition, when manufacturing a cellulose acylate with few low molecular components, it is preferable to adjust the sulfuric acid catalyst amount in an acetylation reaction to 0.5-25 mass parts with respect to 100 mass parts of cellulose. When the amount of the sulfuric acid catalyst is within the above range, cellulose acylate that is preferable in terms of molecular weight distribution (uniform molecular weight distribution) can be synthesized. When used in the production of cellulose acylate that can be used in the present invention, the water content is preferably 2% by mass or less, more preferably 1% by mass or less, and particularly 0.7% by mass. It is a cellulose acylate having a moisture content of not more than%. In general, cellulose acylate contains water and is known to be 2.5 to 5% by mass. In order to make the moisture content of a cellulose acylate into the said range, it is necessary to dry, and the method will not be specifically limited if it becomes the target moisture content. As for the raw material cotton of cellulose acylate and the synthesis method satisfying the above-mentioned various characteristics, pages 7 to 12 are disclosed in JIII Journal of Technical Disclosure (Publication No. 2001-1745, published on March 15, 2001, Invention Association). It is described in detail on the page.

  As a raw material of the cellulose acylate film, a mixture of two or more kinds of cellulose acylates which are in the above-mentioned ranges such as a substituent, a substitution degree, a polymerization degree and a molecular weight distribution can be preferably used.

  The cellulose acylate solution (dope) that can be used for the production of the cellulose acylate film includes various additives (for example, a compound that reduces optical anisotropy, a wavelength dispersion adjusting agent) according to the use in each preparation step. UV inhibitors, plasticizers, deterioration inhibitors, fine particles, optical property modifiers, etc.), which will be described below. Further, the addition may be performed at any time in the dope preparation step, but may be performed by adding a preparation step by adding an additive to the final preparation step of the dope preparation step.

First, a compound that lowers the optical anisotropy of cellulose acylate film, which is one of the additives that can be added to the dope, will be described.
The compound is a compound that suppresses the orientation of the cellulose acylate in the film in the in-plane and film thickness directions, and the optical anisotropy of the film is obtained by adding the compound to the dope to produce a film. Is sufficiently reduced, and a film in which Re is zero and Rth is close to zero can be obtained. Here, being close to zero means, for example, ± 2 nm or less at an arbitrary wavelength. For this purpose, it is advantageous that the compound for reducing the optical anisotropy is sufficiently compatible with cellulose acylate, and the compound itself does not have a rod-like structure or a planar structure. Specifically, when a plurality of planar functional groups such as aromatic groups are provided, a structure having these functional groups in a non-planar rather than the same plane is advantageous.

Among the compounds that suppress the orientation of the cellulose acylate in the film in the plane and in the film thickness direction as described above and reduce the optical anisotropy, the octanol-water partition coefficient (log P value) is 0 to 7 It is preferred to use certain compounds. By adopting a compound having a log P value of 7 or less, compatibility with cellulose acylate is improved, and clouding and powder blowing of the film can be more effectively prevented. Moreover, since the hydrophilicity is high by adopting a compound having a log P value of 0 or more, it is possible to more effectively prevent the water resistance of the cellulose acetate film from deteriorating. A more preferable range for the logP value is 1 to 6, and a particularly preferable range is 1.5 to 5.
The octanol-water partition coefficient (log P value) can be measured by a flask immersion method described in JIS Japanese Industrial Standard Z7260-107 (2000). Further, the octanol-water partition coefficient (log P value) can be estimated by a computational chemical method or an empirical method instead of the actual measurement. As a calculation method, Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27, 21 (1987)), Viswanadhan's fragmentation method (J. Chem. Inf. Comput. Sci., 29,). 163 (1989).), Broto's fragmentation method (Eur. J. Med. Chem.-Chim. Theor., 19, 71 (1984).) And the like are preferably used, but the Crippen's fragmentation method (J. Chem. Inf. Comput. Sci., 27, 21 (1987). When the log P value of a certain compound varies depending on the measurement method or calculation method, it is preferable to determine whether or not the compound is within the scope of the present invention by the Crippen's fragmentation method.

The compound that reduces optical anisotropy may or may not contain an aromatic group. In addition, the compound that decreases the optical anisotropy preferably has a molecular weight of 150 to 3000, more preferably 170 to 2000, and even more preferably 200 to 1000. A specific monomer structure may be used as long as these molecular weights are within the range, and an oligomer structure or a polymer structure in which a plurality of the monomer units are bonded may be used.
The compound that reduces optical anisotropy is preferably a liquid at 25 ° or a solid having a melting point of 25 to 250 °, more preferably a liquid at 25 ° or a melting point of 25 to 200 °. It is a solid. Moreover, it is preferable that the compound which reduces optical anisotropy does not volatilize in the process of dope casting for cellulose acylate film production and drying.

The addition amount of the compound that decreases the optical anisotropy is preferably 0.01 to 30% by mass of the cellulose acylate, more preferably 1 to 25% by mass, and 5 to 20% by mass. Is particularly preferred.
The compound that decreases the optical anisotropy may be used alone, or two or more compounds may be mixed and used in an arbitrary ratio.
The timing for adding the compound for reducing the optical anisotropy may be any time during the dope preparation process, or may be performed at the end of the dope preparation process.

  In the compound that reduces optical anisotropy, the average content of the compound in the portion from the surface on at least one side to 10% of the total film thickness is the average content of the compound in the center of the cellulose acylate film. It is preferable that it exists so that it may become 80 to 99% of. The amount of the compound that reduces the optical anisotropy can be determined by measuring the amount of the compound at the surface and in the central portion, for example, by a method using an infrared absorption spectrum described in JP-A-8-57879.

  Specific examples of the compound that reduces the optical anisotropy of the cellulose acylate film are described in JP-A-2005-309382, [0081] to [0214], and can be used in the present invention. It is not limited.

"adhesive"
The adhesive between the polarizing film and the protective film is not particularly limited, and examples thereof include PVA resin (including modified PVA such as acetoacetyl group, sulfonic acid group, carboxyl group, oxyalkylene group) and boron compound aqueous solution. PVA resin is preferable. The thickness of the adhesive layer is preferably 0.01 to 10 μm, particularly preferably 0.05 to 5 μm after drying.

《Integrated manufacturing process of polarizing film and protective film》
The polarizing plate used in the present invention usually has a drying step in which the polarizing film is stretched and then contracted to reduce the volatile content, but after drying or after the protective film is bonded to at least one surface during drying, It is preferable to have a heating step. In an embodiment in which the protective film also serves as a support for an optical compensation film functioning as an optical compensation layer, a transparent support having a protective film on one side and an optical compensation film on the other side is bonded and then heated. preferable. As a specific application method, during the film drying process, a protective film is applied to the polarizing film with an adhesive while holding both ends, and then both ends are worn, or after drying, polarized from the both ends holding part. There is a method such as releasing the film for film, cutting off both ends of the film, and then attaching a protective film. As a method for cutting off the ears, general techniques such as a method of cutting with a cutter such as a blade or a method of using a laser can be used. After bonding, it is preferable to heat in order to dry the adhesive and improve the polarization performance. The heating condition varies depending on the adhesive, but in the case of an aqueous system, it is preferably 30 ° or more, more preferably 40 to 100 °, and further preferably 50 to 90 °. It is more preferable in terms of performance and production efficiency that these processes are manufactured in a consistent line.

<Performance of polarizing plate>
In order to increase the contrast ratio of the liquid crystal display device of the present invention, it is preferable that the polarizing plate used has a higher transmittance and a higher degree of polarization. The transmittance of the polarizing plate is preferably in the range of 30 to 50%, more preferably in the range of 35 to 50%, and most preferably in the range of 40 to 50% in light having a wavelength of 550 nm. . The degree of polarization is preferably in the range of 90 to 100%, more preferably in the range of 95 to 100%, and most preferably in the range of 99 to 100% in light having a wavelength of 550 nm.
In particular, the optical properties and durability (short-term and long-term storage stability) of the polarizing plate are equivalent to or better than those of commercially available super high contrast products (for example, HLC2-5618 manufactured by Sanlitz Co., Ltd.). It is preferable. Specifically, the visible light transmittance is 42.5% or more, and the degree of polarization {(Tp−Tc) / (Tp + Tc)} ^1/2 ≧ 0.9995 (where Tp is parallel transmittance and Tc is orthogonal transmission) The change rate of the light transmittance before and after being left in a 60 °, 90% humidity RH atmosphere for 500 hours and 80 ° in a dry atmosphere for 500 hours is 3% or less based on the absolute value, Further, it is preferably 1% or less, and the rate of change in polarization degree is preferably 1% or less, more preferably 0.1% or less based on the absolute value.

  The polarizing plate used in the present invention may have an antireflection film whose outermost surface has antifouling properties and scratch resistance. Any conventionally known antireflection film can be used.

[Elliptically polarizing plate]
In the present invention, an elliptically polarizing plate having an optically anisotropic layer may be used. For example, an elliptical polarizing plate in which a protective film, a polarizing film, and the optical compensation sheet are laminated in this order may be disposed in the liquid crystal display device with the optical compensation sheet facing the liquid crystal cell. In the elliptically polarizing plate having such a configuration, the support (polymer film) of the optical compensation sheet also serves as a protective film for the polarizing film. The elliptically polarizing plate is preferably molded into a shape substantially the same as that of the pair of substrates constituting the liquid crystal cell so that it can be incorporated into a liquid crystal display device as it is (for example, if the liquid crystal cell is rectangular, the elliptically polarizing plate). The plate is also preferably molded into the same rectangular shape).

[Backlight]
The liquid crystal display device performs display by turning on and off the light passing through the liquid crystal cell, but when used as a transmission type, a cold cathode or a hot cathode fluorescent tube, or a light emitting diode, a field emission element, an electroluminescent element By arranging a backlight having a light source on the back surface, a bright and vivid display device is obtained.
There are two types of backlights: side-edge type backlights used for display devices used in portable terminals and notebook computers, and direct type backlights used for display devices such as televisions. The side edge type has a shape in which one or two fluorescent lamps are arranged at the end of the light guide plate, and has an advantage that the thickness of the backlight device can be reduced. On the other hand, in the direct backlight, the number of fluorescent lamps can be increased according to the required luminance, and high luminance can be easily obtained. A structure using a light emitting diode, a field emission element, an electroluminescent element or the like instead of the fluorescent lamp in the side edge type and direct type backlights is also effective.
Furthermore, in order to increase the luminous efficiency of the backlight, prismatic or lens-shaped condensing type brightness enhancement sheets (films) are laminated, or polarization reflection type brightness enhancement sheets (films) that improve light loss due to absorption of the polarizing plate. ) May be laminated between the backlight and the liquid crystal cell. In addition, a diffusion sheet (film) for making the light source of the backlight uniform may be laminated, and conversely, a sheet (film) formed by printing a reflection or diffusion pattern for giving an in-plane distribution to the light source. You may laminate. In addition to the backlight that is always lit, there are a backlight that is intermittently lit and a backlight that is divided into a plurality of regions to emit light. It is also possible to adjust the light emission method in association with the image. The backlight may be divided into a plurality of regions, and each may emit different light (brightness and color).

[Field Sequential]
The full color display method using a liquid crystal display device includes a spatial mixing method and a time difference mixing method. The latter is called a field sequential method, and either method is effective.
The spatial mixing method is based on additive color mixing in which light in the red (R), green (G), and blue (B) wavelength regions is superimposed, and in the LCD, pixels that respectively shine in R, G, and B are arranged close to each other. At the same time, by changing the luminance of each pixel, these colors are arbitrarily mixed to obtain any color light. Further, color filters are generally used in the spatial mixing type LCD. However, since the color filter performs color display by absorbing light, the transmittance is low, and the field sequential backlight is superior in terms of power consumption.
The field sequential method is a color display method using a color mixture by “time division”. That is, when two or more colors of light are continuously switched to emit light, and the switching speed is set to exceed the temporal resolution of the human eye, the human can change the above two or more colors. This is a method that applies recognition by mixing colors.
In a field-sequential type full-color LCD, each of the fields in the moving image display has a backlight with one of the R, G, and B emission colors (in some cases, four or more emission colors may be used). In addition to enabling light emission, each color is continuously switched (time-division) for each field to emit light, and an arbitrary color light is obtained by sufficiently increasing the switching speed.

[application]
The liquid crystal display device of the present invention includes an image direct view type, an image projection type, and a light modulation type. The image direct view type is effective for small display devices such as notebook computers, OA devices such as monitors for personal computers, multimedia displays such as televisions, car navigation systems, mobile phones, portable terminals, clock-type terminals, and wearable displays. Furthermore, it is also effective for display devices for amusement devices and large display devices for vertical or floor use for meetings.
The image projection type includes a front projector type that projects directly onto the screen and a rear projector type that projects from the back of the screen. It is also effective for a portable projector using an LED light source or the like.
The light modulation type is effective for a display device called a three-dimensional display or a highly realistic display. For example, it is effective for a three-dimensional display using two liquid crystal cells and a cylindrical three-dimensional display composed of a plurality of rear projectors.

  The present invention will be described more specifically with reference to the following examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

<Production of IPS mode liquid crystal cell>
On one glass substrate, electrodes were arranged so that the distance between adjacent electrodes was 20 μm, and a polyimide film was provided as an alignment film thereon, and a rubbing treatment was performed. A polyimide film was provided on one surface of a separately prepared glass substrate, and a rubbing treatment was performed to obtain an alignment film. The two glass substrates are stacked and bonded so that the alignment films face each other, the distance between the substrates (gap; d) is 4.0 μm, and the rubbing directions of the two glass substrates are parallel. A nematic liquid crystal composition having a refractive index anisotropy (Δn) of 0.0769 and a dielectric anisotropy (Δε) of 4.5 was enclosed. The value of d · Δn of the liquid crystal layer was 310 nm.

<Preparation of polarizing film>
After washing both surfaces of the PVA film with ion-exchanged water at a flow rate of 2 liters / minute, air blowing to remove surface moisture and reducing the amount of foreign matter adhering to the surface to 0.5% or less, the PVA film is then treated with iodine. After dipping in an aqueous solution of 1.0 g / liter and potassium iodide 60.0 g / liter at 25 ° for 90 seconds, and further immersed in an aqueous solution of boric acid 40 g / liter and potassium iodide 30 g / liter at 25 ° C. for 120 seconds , Introduced into a tenter stretching machine, once stretched to 7.0 times in an atmosphere of 40 ° C. and 95%, contracted to 5.3 times, kept constant in width after that, dried at 60 ° C. and then detached from the tenter did. The moisture content of the PVA film before starting stretching was 30%, and the moisture content after drying was 1.5%. Further, the elastic modulus of the PVA film before stretching was 35 Mpa in an atmosphere of 40 ° C. and 95%.

[Example 1]
(Preparation of polarizing plate)
The upper polarizing plate uses an acrylic adhesive to absorb cellulose acylate film (Re = 0.5 nm, Rth = 0.2 nm) on both sides of the polarizing film prepared above, and absorbs the slow axis and the polarizing film. Adhesion was made so that the shaft was parallel.
The lower polarizing plate was prepared by adhering a cellulose acylate film (Re = 0.5 nm, Rth = 0.2 nm) on both sides of the polarizing film prepared above using an acrylic adhesive. The protective film was laminated by crossing the slow axis of the protective film and the polarizing film absorption axis within ± 2 °.

(Production of liquid crystal display device)
A liquid crystal display device was produced by laminating polarizing plates on both sides of the liquid crystal cell with an adhesive. The polarizing plate on the viewing side (upper polarizing plate) was laminated so that the extraordinary refractive index direction of the liquid crystal composition in the liquid crystal cell and the absorption axis of the polarizing plate were orthogonal when no voltage was applied. Further, the absorption axes of polarizing plates on the viewing side and the backlight side were arranged to be orthogonal to each other.

(Production of color filter)
A color filter was formed on the surface of one of the two glass substrates constituting the liquid crystal cell using a transcer color filter manufactured by Fuji Photo Film Co., Ltd. by the method described in JP-A-10-221518. . The surface irregularity of the Transer color filter was 0.2 microns or less.
At this time, by changing the thickness of each color of the blue, green and red color filters, the retardation Rth in the thickness direction of each colored layer is changed, so that the Rth of the blue layer (450 nm) is 8 nm and the Rth of the green layer (550 nm). Was 1 nm, and Rth of the red layer (650 nm) was 5 nm.

(Optical performance of liquid crystal display)
The manufactured liquid crystal display device is placed on a field sequential backlight composed of RGB three-color LED light sources, a white display voltage of 2 V and a black display voltage of 5 V are applied to the liquid crystal cell, and a luminance meter (SR-3 manufactured by Topcon Corporation) is used. Then, the contrast ratio (ratio between white display transmittance and black display transmittance) of the front of the panel and the black transmittance at an azimuth angle of 0 to 360 ° at a polar angle of 60 ° and an interval of 5 ° are measured, and the maximum transmittance is measured. Is shown in Table 1. From the results in the table, there was little leakage light in blue, green and red displays, and there was little coloring when observed from an oblique direction.

[Example 2]
In Example 1, the thickness of each color of the blue, green and red color filters is changed to change the retardation Rth in the thickness direction of each colored layer. The Rth of the blue layer (450 nm) is 12 nm and the green layer (550 nm) The Rth was 5 nm, the Rth of the red layer (650 nm) was 15 nm, and the other configurations were the same.
Compared with the liquid crystal display device of Example 1, the liquid crystal display device of this example further decreased the oblique transmittance in each color, and the coloring was improved.

[Comparative example]
In Example 1, measurement was performed without stacking color filters, and leakage light of each color was similarly observed. The results are shown in Table 1. From the results shown in the same table, it can be understood that, particularly, the red transmittance at the time of the black marking is large and the color is red.

It is the schematic which shows an example of the liquid crystal display device of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention.

Explanation of symbols

1 Upper polarizing plate protective film 2 Slow axis direction of upper polarizing plate protective film 3 Upper polarizing plate polarizing film 4 Upper polarizing plate polarizing film absorption axis 5 Upper polarizing plate liquid crystal cell side protective film 6 Upper polarizing plate liquid crystal cell side protective film Slow axis direction 7 Optical anisotropic film 8 Optical anisotropic film slow axis 9 Liquid crystal cell upper substrate 10 Upper substrate rubbing direction 11 for liquid crystal alignment Liquid crystal molecule (liquid crystal layer)
12 Liquid crystal cell lower substrate 13 Lower substrate Liquid crystal alignment rubbing direction 14 Lower polarizer liquid crystal cell side protective film 15 Lower polarizer liquid crystal cell side protective film slow axis direction 16 Lower polarizer polarizing film 17 Lower side Absorption axis 18 of polarizing plate polarizing film Lower polarizing plate protective film 19 Slow axis direction 20 of lower polarizing plate protective film Backlight unit 20a Light source lamp 21 Upper polarizing plate 22 Lower polarizing plate 23, 23 'Applied electric field direction 24 Linear electrode 25 Insulating layer 26 Electrode

Claims (4)

An electric field including at least one pair of substrates having electrodes arranged opposite to each other and a liquid crystal layer disposed between the substrates and controlled in alignment, and containing the component parallel to the substrate having the electrodes by the electrodes. A liquid crystal display device, and a liquid crystal display device having at least a pair of polarizing plates arranged with the liquid crystal layer interposed therebetween, wherein the liquid crystal cell includes three pixel regions and three pixel region Rth of color filters arranged on at least two pixel regions among the color filters arranged on the three pixel regions are different from each other.
When the main wavelengths taking the maximum transmittance of the color filters arranged on the three pixel regions are λ ₁ , λ ₂ and λ ₃ (unit: nm) in order from the smallest, Rth of the color filter is as follows: Satisfy formulas (I) and (II),
Formula (I): Rth (λ ₃ )> Rth (λ ₂ )
Formula (II): Rth (λ ₁ )> Rth (λ ₂ );
And the color filter satisfies the following formulas (III) and (IV): (III) 0 ≦ Re (630) ≦ 10 and | Rth (630) | ≦ 25
(IV) | Re (400) −Re (700) | ≦ 10 and | Rth (400) −Rth (700) | ≦ 35
(In the above formulas (I) and (II), Re (λ) represents the front retardation value (nm) at the wavelength λnm, and Rth (λ) represents the retardation value (nm) in the film thickness direction at the wavelength λnm. .)
A liquid crystal display device characterized by the above. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is in an IPS mode or an FFS mode. The liquid crystal display device according to claim 1, wherein an electric field including a component parallel to the substrate is generated by a pair of electrodes at least one of which is arranged in different layers and is transparent.   Both of the pair of polarizing plates have a polarizing film and a protective film provided on at least one surface of the polarizing film, and the protective film is disposed between the liquid crystal cell and the polarizing film. The liquid crystal display device according to claim 1, wherein the liquid crystal display device is a liquid crystal display device.

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